Related Experiment Videos
In vivo expression of single-stranded DNA in mammalian cells with DNA enzyme sequences targeted to C-raf
Abstract:
The use of antisense oligodeoxynucleotides (AS-ODN) remains a viable method to downregulate selected gene function. However, limitations to the antisense approach remain, such as (1) difficulties in delivery of the AS-ODN into target tissues, (2) instability of AS-ODN in vivo, (3) uncertanties about the precise mode of action, and (4) toxic effects in animal and human studies. To circumvent some of these difficulties, we designed a vector set that directs the in vivo production of single-stranded DNA (ssDNA) of a desired target sequence with limited extraneous vector nucleotide sequences. One plasmid was designed to express Moloney murine leukemia virus (MoMuLV) reverse transcriptase (RT). Another expression plasmid contains the MoMuLV primer binding site at the 3'-end of its RNA transcript so that an ssDNA would be synthesized by RT when both plasmids are cotransfected into cells. To test this expression system, we constructed a plasmid set, pssXA/pssXB that produces ssRNA-cleaving DNA 10-23 enzyme (Santoro, S.W., and Joyce, G.F. [1997]. Proc. Natl. Acad. Sci. USA 37, 13330-13342). The DNA enzyme sequence was placed between two oligonucleotide arms that are complementary and able to specifically target C-raf kinase mRNA. These plasmids were transfected into the A549 lung carcinoma cell line. Reduced C-raf mRNA levels by up to 34%-36%, as determined by Northern blot analysis, were observed in the transfected cells. Our results demonstrate the feasibility of using this novel ssDNA expression system to generate any sequence of interest in vivo for antisense, RNA-cleavage DNA enzyme, or triplex-forming strategies.
Insights
This study introduces a novel single-stranded DNA (ssDNA) expression system to overcome limitations of antisense oligodeoxynucleotides (AS-ODN). The system successfully reduced C-raf kinase mRNA levels in lung cancer cells, demonstrating its potential for gene regulation strategies.
Area of Science:
- Molecular Biology
- Gene Regulation
- Biotechnology
Background:
- Antisense oligodeoxynucleotides (AS-ODN) are effective for gene silencing but face challenges in delivery, stability, mechanism, and toxicity.
- Existing methods require improvements to enhance in vivo efficacy and safety.
Purpose of the Study:
- To develop and validate a novel vector system for in vivo production of single-stranded DNA (ssDNA).
- To circumvent limitations associated with traditional AS-ODN approaches.
- To demonstrate the feasibility of using this system for gene-specific targeting.
Main Methods:
- Co-transfection of two expression plasmids into A549 lung carcinoma cells.
- One plasmid expresses Moloney murine leukemia virus (MoMuLV) reverse transcriptase (RT).
- The second plasmid contains the MoMuLV primer binding site for ssDNA synthesis, encoding a C-raf kinase-targeting DNA enzyme.
Main Results:
- The novel ssDNA expression system successfully generated a DNA enzyme targeting C-raf kinase mRNA.
- Northern blot analysis revealed a 34%-36% reduction in C-raf mRNA levels in transfected cells.
- The system demonstrated feasibility for generating specific ssDNA sequences in vivo.
Conclusions:
- The developed ssDNA expression system is a viable strategy to overcome AS-ODN limitations.
- This technology enables in vivo generation of specific DNA sequences for various gene modulation applications.
- The system shows promise for antisense, DNA enzyme, and triplex-forming strategies.